According to new research published in the Journal of Clinical Investigation, tumours associated with melanoma patients cause the body's immune response to weaken to a point where it's not able to kill cancerous cells within the tumour. The team of researchers, led by Dr Sophia Karagiannis and Professor Frank Nestle at King's College London, UK, also detected a potential antibody biomarker which could help in determining the type of treatment best for different people.

Previous researches have indicated that specific antibodies are generated in melanoma patients that attack cancer cells. Although, the immune response of the patient is often unable to prevent the cancer from spreading to nearby cells. The most common antibody produced by the body's immune system the class "IgG". The most effective antibodies which are produced are of IgG1 subclass, while the least efficient are the IgG4 subclass. The study was done on 80 different patients in the clinic of St John's Institute of Dermatology at Guy's and St Thomas' NHS Foundation Trust, London.
Researchers found that melanoma tumours attract IgG4 antibodies - the weakest immune response - and interfere with the circulating IgG1 antibodies.

Dr Karagiannis added:

"We were able to mimic the conditions created by melanoma tumours and showed that B cells can be polarised to produce IgG4 antibodies in the presence of cancer cells."

The immune response of the body was found normal in the presence of healthy cells with IgG1 antibodies as the most common. Researchers also found that IgG4 wasn't as efficient as IgG1 in triggering immune cells to kill cancer cells. Additionally , IgG4 prevented the IgG1 antibody from effectively killing tumour cells. Patients with high IgG4 levels in their blood tended to have a worse prognosis than with normal levels of the antibody. This indicates that IgG4 could indicate disease progression.

Dr Karagiannis said: "This work bears important implications for future therapies since not only are IgG4 antibodies ineffective in activating immune cells to kill tumours but they also work by blocking antibodies from killing tumour cells. The latter means that IgG4 not only prevents the patient's more powerful antibodies from eradicating cancer, but could also explain why treatments may be hindered by those native IgG4 antibodies found in patients, making therapeutic antibodies less effective."